BCECE Engineering BCECE Engineering Solved Paper-2001

  • question_answer
    Reactance of a capacitor of capacitance\[C\mu F\] for AC frequency\[\frac{400}{\pi }\]0 Hz is\[25\,\Omega .\]The value of C is:

    A)  \[50\,\mu F\]    

    B)                        \[25\,\mu F\]                    

    C)  \[100\,\mu F\]                

    D)        \[75\,\mu F\]

    Correct Answer: A

    Solution :

    Capacitive reactance of an AC circuit containing only capacitor with an AC source is \[{{X}_{C}}=\frac{1}{\omega C}\] or            \[{{X}_{C}}=\frac{1}{2\pi \,f\,C}\] or            \[C=\frac{1}{2\pi \,f\,{{X}_{C}}}\] Here,     \[f=\frac{400}{\pi }Hz,\,{{X}_{C}}=25\,\Omega \] \[\therefore \]  \[C=\frac{1}{2\pi \times \frac{400}{\pi }\times 25}=\frac{1}{2\times 400\times 25}\] \[=5\times {{10}^{-5}}\,F\] \[=50\,\mu F\]


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